I finally managed to get my OEM 11/23+ to boot from the RL02 today, the solution to the OEM boot ROM problem was to set the RLV12 addressing mode to 18 bit, rather than 22bit. I assume that this is a feature of the OEM boot program :-) I'm now getting garbage on the terminal, but have yet to figure out which setting I've got wrong! Jim. Please see our website the " Vintage Communication Pages" at WWW.G1JBG.CO.UK